Human beings have used the impact of water flow to create hydraulic machinery such as waterwheels and watermills since ancient times. If water is sprayed from a high-pressure water gun, its impact will be greater. It was used in the coal mining industry in the former Soviet Union and was called hydraulic coal mining. The high-speed jet of water is blocked by the coal seam, and the speed drops suddenly. In an instant, a large enough impact force is generated to cause the coal seam to brittlely fracture, completing the coal mining operation. Inspired by this, scientists from the former Soviet Union developed high-pressure water jet cutting technology, and an American company patented this technology and commercialized it.
Ordinary water passes through an ultra-high pressure pressurizer to pressurize the water to 4,000 bar (60,000 psi), and then passes through a small nozzle (its diameter is 0.004 inches to 0.016 inches). Produces a water arrow that reaches 915 meters per second (about three times the speed of sound). This water arrow can perform various surface treatments and cut various non-metallic materials such as paper, diapers, glass, fibers, sponges, etc.
For cutting metal and hard materials such as various stones, glass, ceramics, tiles, etc., Fulu has developed a patented and more complete design, which is to combine sand and water. The arrows are mixed to enhance their cutting capabilities. This high-speed abrasive waterjet can cut almost any material.
To achieve this, there is a relatively high demand for water, pipes, and spouts. Such as pipes, water jets use high-pressure tools to pressurize water and shoot it out. It must have extremely high pressure to cut through hard cutting materials, so the pipeline must be able to withstand extremely high pressure. This pressure is far greater than 700 megawatts. Pa, because the thin steel plate (the material being cut) itself can withstand a pressure of 700 MPa.
Secondly, it is wrong that the water used for water jets has no impurities at all. Because the water pressure is much greater than 700 MPa, for sealing equipment such as pipelines, no matter how good the sealing performance is, pure water will always cause them to wear and leak. In order to solve this problem, 5% of soluble emulsified oil must be added to the water jet water to improve the sealing effect. For high-pressure pumps, some oil should also be added to improve its sealing performance.
As mentioned above, the water jet nozzle is made of carbide, sapphire and other materials. The diameter of the nozzle is only 0.05 mm, and the inner wall of the hole is smooth and flat, and can withstand a pressure of 1700 MPa, so The high-pressure water sprayed out can cut the material like a knife. Some water is also added with long-chain polymers, such as polyethylene oxide, to increase the "viscosity" of the water and make the sprayed water look like a "thin line."
Its processing accuracy is high, the cutting width is only 0.1-0.8 mm, and it can process parts with complex shapes. The cuts of the processed parts are smooth and neat, and no trimming is required. Especially for the processing of materials that are prone to thermal deformation, "water jet" has unique advantages.
It does not have wear problems like cutting tools. The abrasives and wastewater mixed in the water jet can be recycled and used. The equipment is relatively simple and the processing cost is low. The vibration and noise caused during the processing are very small, and the amount of chips is only 15-20 times that of mechanical processing. The chips flow away with the water and will not fly and harm the operator.
The "water knife", precisely because it is not a knife, has opened up a broad field of use. Cutting composite materials is a difficult problem in processing. If traditional processing methods are used, delamination and tearing will occur, and the "water jet" is the ideal tool to solve this problem. Using a "water jet" to remove ceramic coatings from components is more effective than mechanical and chemical methods. "Water jet" can be used to punch holes and crush materials. It is also very convenient to use a "water jet" to clean the attachments on the surface of the hull and propeller, and the scale in the chemical pipelines.
"Waterjet" can also be used in surgical operations. [The University of Tokyo School of Medicine used a "water jet" with a pressure of 0.7 MPa to conduct experiments on rabbits, which showed that it can be used for operations on liver, kidney and other organs without damaging surrounding tissues and not easily causing infection. 〕